Automatic lifting grab



Sept. 30', 1924. 1,510,176

s. c. KNIGHT AUTOMATIC LIFTING GRAB Filed June 30, 1922 3 Sheets-Sheet lg 28 FIG. 1. l

FIG. 3.

Susan-V NVE/VTOR;

ATTy.

S. C. KNIGHT AUTOMATIC LIFTING GRAB Se t. 30 1924.

Filed June 50, 1922 3 Sheets-Shaet 2 vl IL PIC-3.6.

N YE/VTORZ L 7 77 Wm WM ATTY.

Sept. 30, 1924.

S. C. KNIGHT AUTOMATIC LIF'I'ING GRAB Filed June 30, 1922 3 Shan -Sheet5 b.. urvv FIG. 7.

i atented Sept. 30, 1924;

UNITED STATES STANLEY CHRISTIE KNIGHT, OF GOSFORTH, ENGLAND.

AUTOMATIC LIF'IING GRAB.

Application filed June 30, 1922. Serial No. 572,000.

To all 107mm it may concern:

Be it known that I, STANLEY CHRISTIE Kmcrrr, a subject of the King ofGreat liritain and Ireland, residing at Gosforth, in the county ofNorthumberland, England, have invented new and useful Improvements inAutomatic Lifting Grabs, of which the following is a specification.

This invention relates to automatic grabs for lifting plates, girders,bars, shells, bar- I'cls, rectangular cases and other bodies, and hasfor its object to provide an improved construction.

In an automatic lifting grab in accordance with my invention relativemovement occurs, when the grab engages the body to be raised, betweenthe frame of the grab wherein the gripping jaws are mounted and themember with which the lifting tackle co-acts and which takes the weightof said body, and said relative movement in one direction is utilizedthrough levers to cause the jaws to approach and grip the body, thegripping power being proportional to the weight of the body beingraised, relative movement between said parts in the reverse directionwhen the grab is lowered and the body is supported by the ground orotherwise retracting the jaws and releasing the body. Means may beprovided whereby the retraction of the jaws and consequent release ofthe body is prevented until desired.

I will more fully describe my invention with reference to theaccompanying draw iugs wherein a Figure 1 is an elevation of aplate-lifting grab constructed in accordance with my invention, one sideof the frame being removed for clearness;

Figure 2 is a section on the line XX in Fig. 1 to a larger scale;

Figure 3 is a section on the line Y-Y in Fig. 2; and

Figure 4 is a part similar view to Fig. 1 illustrating the parts in thegripping position.

Figures 5 and 6 are two elevations at right angles of a barrel-liftinggrab constructed in accordance with my invention; and

Figure 7 is a part central section to a larger scale.

. Referring first to Figs. 1 to 4 of the accompanying drawings, thelifting grab therein illustrated is intended for lifting steel or likeplates or slabs of marble, slate or stone. In this example the grippingjaws 10 are pivoted at 11 to the inner ends of two oppositely-disposedlevers 12 pivoted at 13 between the side members 14 of the frame, theouter ends of the levers 12 carrying pins 15 working in slots 16 in theouter ends of pairs of levers 17 pivoted at 18 between the frame members14 and having slots 19 at their inner ends (which cross) engaging pins20 projecting from a central block 21, the arrangement being such thatupward movement of the block 21 moves the jaws 10 together and downwardmovement of said block moves the jaws apart, said movements of the blockbeing in relation to the frame 14. The block 21 is provided with acentral downward extension 22 adapted to engage the upper edge of theplate to be lifted and is guided in the frame members 14 by theengagement of the block 21 with a vertical spindle 23 carried by crossbars 24 mounted between the frame members 14 and by the engagement ofthe pins 20 with ribs 25 on the inside of the frame members 14. Theblock 21 and extension 22 are hollow, and passing through them is acentral spindle 26 which normally projects below the extension 22. Thespindle 26 has a head 27. The lifting tackle 28 is attached to a collar29 loose on the spindle 26 and normally resting on the upper cross bar24.

The collar 29 is provided with opposite one-way catches 30 mounted onoppositelysliding plates 31. When the catches 30 are projected theyengage stops 30 on the frame members 14, but they are adapted to beretracted by side bars 32 attached by pivoted links 33 (Fig. 2) to thespindle 26 and at their bottom ends by links 34 to feet 35 engagingrecesses in the block 21 whereby said bars are anchored to the block,movement of the spindle 26 relative to the block 21 (which occurs whenthe spindle 26 engages the top of the plate to be lifted), moving saidbars outwards and, through the sliding plates 31, retracting the one-waycatches 30 against the action of springs 36 (Fig. 3) attached at one endto the plates 31 and at the other to the collar 29. It will be seenthatthe right hand bar 32 retracts the left hand catch (and vice versa), thebars engaging pivoted projections 31 on the plates 31, said projectionsbeing mounted so that they are free to turn up on their pivots againstthe action of springs 31".

In use, the grab is lowered onto the plate which is indicated at 37 inFig. 4, so that the jaws 10 He en either side thereof, the weight of thegrab being supported by the lifting tackle 28 through the one-waycatches 30 which engage'the stops 30' on the frame members 14. When thelower end of the spindle 26 engages the upper edge of the plate 37, thespindle is moved upwards relatively to the block 21 and the catches 30are retracted by the consequent outward movement of the bars 32 anddisengaged from the stops 30. The downward extension 22 of the blockthen engages the upper edge of the plate 37, and as the downwardmovement of the grab continues, the consequent upward movement of theblock relatively to the frame causes the levers 17, 12 to move the jaws10 together to grip the plate 37 between them. The grab can now beraised. Upward move ment of the lifting tackle 28 lifts the collar 29past the stops 30 (the catches 30 being still retracted) into engagementwith the head 27 of the spindle 26. This is-the position illustrated inFig. 4. Further upward movement of the lifting tackle picks up the grabwith'the plate 37 securely held .be-

' tween the jaws 10. On the grab being subsequently ,lowered until theplate 37 is supported by the ground or otherwise and the downwardmovement of the lifting tackle being continued, the collar 29 falls onthe spindle 26, the pivoted projections 31 turning up when they strikethe tops of the side bars 32 so that the catches 30 are not retracted bysaid bars although the bars are still in the extended position. Theone-way catches 30 pass the stops 30 as the collar falls. When thelifting tackle is again raised, the catches 3O engage the stops 30 andthe frame is raised but the weight of the block 21 keeps its downwardextension in engagement with the upper edge of the plate 37 until theframe 14 has moved upwards relatively to the block which movement,through the levers 17, 12, causes the jaws 10 to disengage the plate. Asthe grab leaves gie plate 37, the block 21 and spindle 26 r urn to theirnormal positions and the bars 32 are retracted allowing the pivotedprojections 31 to resume their original position.

If desired, a rack 38 (Figs. 1 and 4) may be provided, said rack beingcarried by cross members 39 between the frame members 14.

and a spring pawl 40 mounted upon the block 21, said pawl permittinupward movement of the block relative y to the frame but automaticallylocking the block in its raised position until said pawl isdisengagedfrom the rack 38 by pulling a chain 41. Where this rack andpawl is fitted, the plate 37 will not be automatically disengaged uponbeing supported by the ground or otherwise when the grab is raisedagain. Disengagement of the plate 37 will not occur until the pawl 40 isdisengaged from the rack 38.

Figures 5 to 7 illustrate a modified construction of, grab intended forlifting barrels. In this example the jaws 10 are pivoted at 11 betweenthe lower ends of the side members 14 of the frame and are provided withtail pieces 42 pivoted at 43 to links 44 pivoted to a block 21 slidingon the centre spindle. 26 so that upward movement of the block 21 movesthe jaws 10 together and downward movement of said block moves the jawsapart said movement of the block being in relation to the frame 14. Thelifting tackle is attached to a shackle 28 bolted to the collar 29 looseon the spindle 26. In a slot 45 in the spindle 26 is pivloted a catch 46which is weighted at its upper end and provided at its lower end. with astep 47 adapted to engage the bottom of 'a sleeve 48 loose on thespindle 26. Normally the lower end of thecatch 46 lies within the boreof the block 21. A flange 49 around. the top of said sleeve engagesstops 50 on the frame members 14 and limits the downward travel of saidsleeve. The sleeve 48 is goned internally as shown at 51 (Fig. 7), andsaid coned portion coacts with pawls 52 pivoted at 53 to the collar 29,said pawls normally engaging stops 54 on the frame members 14.

In use, the grab is suspended by the shackle 28, the frame 14 beinsupported by the engagement of the paw s 52 with the stops 54 as shown,the lower end of the spindle 26 projecting below its frame. The grab islowered onto the barrel to be lifted so that the jaws 10 embrace saidbarrel. The lower end of the spindle 26 comes against the top of thebarrel, and, the downward movement of the grab continuing, the spindle26 rises relatively to the frame. This upward movement of the spindledisengages the lower end of the catch 46 from the bars of the block 21,and, by reason of the greater weight of the upper end of said catch, itslower end is projected beyond the spindle 26 whereby the step 47 thereonis caused to engage the bottom of the loose sleeve 48. A spring may, ifdesired, be provided behind the catch 46 to project its lower end whenit clears the bore of the block 21. Simultaneously therewith theenlarged lower end of the spindle 26 picks up the block 21 and, theupward movement of Ill) the spindle 26 relative to the frame 14continuing, the jaws 10 are moved together to grip the barrel by theco-action of the links 44 with their tail pieces 42, and the conedinternal face 51 of the sleeve 48 disengages the pawls 52 from theirstops 54 thus freeing the collar 29 from the frame. The grab can now beraised. On the grab-being lifted, the collar 29 engages the head 27 ofthe spindle 26, the lower end 'of said spindle keeping the block 21 inits ralsed pos1t1on whereby the jaws 10 are caused to grip the barrel.Upon subsequently lowering the grab until the barrel rests on the groundor otherwise, the collar 29, the block 21 and the sleeve 48 will allmove downwards relatively to the frame and the parts will resume theirnormal positions with the pawls 52 engag ing their stops 54 so that,when the grab is again lifted, the collar 29 will be locked by the pawls52 to the frame and the jaws will disengage the barrel and be liftedclear away therefrom.

While I have described as examples of lifting grabs in accordance withmy invention, a grab for lifting plates and one for lifting barrels, bysuitably modifying the shape and travel of the lifting jaws, the grabsmay be adapted for liftin girders, bars, shells, rectangular cases andother bodies. I may suspend a number of lifting grabs from a frameworkwhereby they are retained in suitable relative positions, said frameworkbeing ada .rted to be raised and lowered by lifting tac kle, said grabssimultaneously engaging, gripping, raising, lowering and releasing acorresponding number of plates, barrels or other bodies.

By my invention I provide a grab which is entirely automatic in action,and which is locked in the gripping position before the plate or barrelor other body is raised from the ground. My improved grab actsimmediately it is lowered onto the plate, barrel or body to be lifted,and releases same immediately the load is taken off the grab (exceptwhere the grab is provided with a rack and pawl locking arrangement ashereinbefore described). It does not require to be locked or re-set byhand and is therefore fool-proof. Working automatically and without theneed of an attendant, my improved grab may be used for picking upred-hot ingots or for similar purposes where it is not possible for aworkman to be near, the jaws and adjacent parts of the grab beingsuitably protected from the heat;

I wish it to be understood that the details and arrangements of themembers of my improved automatic lifting grabs may be modified withoutdeparting from the spirit of my invention.

What I claim as my invention and desire to secure by Letters Patentis 1. An automatic lifting grab comprising a frame, jaws ivoted theretoadapted to grip the body to be lifted, a member capable of movementrelatively to said frame, pivoted links connecting said member to saidjaws, and lifting tackle connected to said member, relative movement inone direction between said member and frame causing the jaws to approachand grip the body which movement automatically occurs when the grabengages the body, and relative movement in the reverse direction betweensaid member and frame causing the jaws to retract and release the bodywhich reverse movement automatically occurs when the weight of the bodyis taken off the grab.

2. An automatic lifting grab com rising a frame, jaws pivoted theretoadapte Y to grip the body to be lifted, a. member capable of movementrelatively to said frame, pivoted links connecting said member to saidjaws, lifting tackle connected to said member, relative movement in onedirection between said member and frame causing the jaws to approach andgrip the body and relative movement in the reverse direction betweensaid member and frame causing the jaws to retract and release the body,and .means whereby the retraction of the jaws and consequent release ofthe body is prevented until desired.

3. An automatic lifting grab comprising a frame, a pair ofoppositely-disposed levers pivoted thereto, gripping jaws carried bysaid levers, a central spindle capable of movement relatively to saidframe, a collar loose on said spindle, lifting tackle attached to saidcollar, a block loose on said spindle, pivoted links connecting saidblock to the aw-carrying levers, relative movement in one directionbetween said block and said framecausing the jaws to approach and in thereverse direction retracting said jaws, means for locking the collar tothe frame, and means actuated by the relative movement between thespindle and the block for retracting said locking means when the spindleengages the body to be lifted and for re-locking the collar to the framewhen the grab is lowered and the jaws are relieved of the weight of thebody.

4. An automatic lifting grab comprising a frame, a pair ofoppositely-disposed levers pivoted there-to, gripping jaws carried bysaid levers, a central spindle capable of movement relatively to saidframe, a collar loose on said spindle, lifting tackle attached to saidcollar, a block loose on said spindle, pivoted links connectingv saidblock to the jaw-carrying levers, relative movement in one directionbetween, said block and said frame causing the jaws to approach and inthe reverse direction retracting said jaws, means for locking the collarto the frame, means actuated by the relative movement between thespindle and the block for retracting said locking means when the spindleenosition when the gages the body to be lifted and for re-lockmgthe-collar to the frame when the grab is lowered and the jaws arerelieved of the weight of the body, a rack on the frame and. a springawl on the block (or vice versa) whereby t e return of said block tonormal b' is lowered and the aws are relieved of tl ie wei ht of thebody is prevented until said paw is disengaged 10 from said rack byhand.

In testimony whereof I have signal my name to this specification.

STANLEY CHRISTIE KNIGHT.

